Whether you want to top up your knowledge on a subject or learn a completely new skill, there is no shortage of online courses to help you on your way. In fact, there are so many choices, it can be difficult to figure out which platform suits you best!

To help you navigate the rapidly expanding world of online education, here are 10 of the most popular options for upgrading your skills.

Coursera

Coursera has partnered with leading universities in the U.S. and around the world to provide online courses covering dozens of different subjects. Recently, they’ve introduced “specializations”—10 different course pathways that will lead to an official certification from an associated university.

Coursera has a wide diversity of subjects available to choose from; everything from data science to musical theory. As Coursera prides itself on being accessible to everyone, many of the courses are either free or very cheap to to take, with only the official certification at the end having a higher cost involved.

Lynda,com

A veteran in the online education space, Lynda.com offers a subscription-based video tutorial library. Think of it as an education-based Netflix. A great option for people who are visual learners, and at a reasonable cost of $25 per month, a Lynda.com membership provides unlimited access to more than 80,000 videos on a broad range of different subjects.

Udemy

With an average of 800 new courses added to their repertoire every month, Udemy is a bit more expensive than its competitors. Costs vary broadly, ranging from $10 to $500 for different courses; the most popular Udemy courses in business and technology tend to be upwards of $100. However, you can read the reviews of former students before signing up to any of the courses, so you can make a more informed decision.

Udacity

Udacity is a platform with a strong focus on technology, with a small but well-crafted selection of courses. If you’re looking to break into data science (called the “sexiest job of the 21st century“), Udacity’s data science program has an impressive roster of teachers from companies like Salesforce and Facebook.

Udacity’s pricing structure allows you to pay monthly for your courses; if you decide to drop a program before completing it, you pay for the course up to that point, rather than the whole thing.

Khan Academy

Khan Academy is a non-profit online platform providing a completely free library of educational “micro-lectures.” Focusing on more traditional academic subjects, Khan Academy provides a mix of video and text-based materials in math, science, economics, humanities, and a bit of computer programming. Since Khan Academy is free for anyone to use, it’s a great to way to get a taste for a subject before moving onto a more advanced course elsewhere.

Codecademy

Previously backed by the White House, Codecademy is dedicated to teaching people how to code—and it’s available for free. While other online coding courses are a “learn at your own pace” environment, Codecademy motivates learners to keep a fast pace using supportive groups and a gamified points system.

The school offers courses on a number of languages—including PHP, Phython and Ruby—and students are often already building and deploying projects by the time they finish their course.

Bloc

Focused on web development, Bloc is a more intensive option for those who want to learn quickly. Instead of short courses or lectures, this highly structured program runs for 25 hours per week over several months. With tuition starting at $4,250, bloc.io doesn’t come cheap—but it does offer a great option for those who are ready to commit to a career change.

Iversity

Hailed as the “Coursera of Europe,” Berlin-based iversity has partnered with European and international universities to offer academic courses for free. Unlike Coursera, however, it doesn’t look like iversity is currently providing any official certification.

Skillshare is a community marketplace for new skills. With a broad range of different subjects to choose from, Skillshare offers an online catalog of video-based courses, as well as in-person workshops in cities like San Francisco and New York.

Many classes are available to take without a membership at a cost of around $20-$30 each, but top classes—taught by industry leaders—are only available with a Skillshare membership. Membership costs $9.95 per month and, while it doesn’t get you any free content, it does provide 20 percent off of all classes. Like other platforms, Skillshare provides student reviews for your reference.

General Assembly

Focusing on education in design, business and technology, New York City-based General Assembly has campuses in nearly a dozen different cities around the world. Although the majority of General Assembly classes are in-person, they also offer a compact selection of online-only or mixed courses.

General Assembly even livestreams popular lectures, providing real-time interaction with the lecturer and other students. Their online courses range in price, from one-off lectures to multi-part workshops.